Photometers and Radiometers

UDT Instruments, a division of Gamma Scientific, offers an extensive selection of photometers, lux meters, luminance meters, illuminance meters and optical sensors to meet your photometric test and measurement needs.

Our photometric sensors are designed with the most accurate photometric filters in the world to accurately match the human eye response.

Combining our wide range of optometers, photometric sensors and accessories, with our state-of-the-art calibration facilities, allows our applications engineers to assemble and configure custom photometer systems for nearly any project.


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System Configuration Guide

Learn how to configure a photometer or radiometer system to meet your testing requirements with this free guide from Gamma Scientific.


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Guide to Photometry

What’s in the Guide?

  • Definitions of the most important terms in photometry
  • Photometric to radiometric conversion factors
  • How to specify a photometer system
  • Photometric quantity units, symbols and abbreviations


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Handheld Photometers

We offer two high-accuracy handheld photometers for use in laboratory settings or field environments. Both instruments are compatible with the full range of UDT Instruments sensor heads and are calibrated in our ISO-17025 accredited laboratory.

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Benchtop Photometers

The UDT Instruments flexOptometer is a high-performance photometer available with a single head or with up to four interchangeable detector heads for optimal flexibility. If your application requires measurement of low light levels, our C Series flexOptometers offer ten times greater sensitivity than standard flexOptometer systems.

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Luminance Meters

We manufacture a variety of luminance meter systems (both handheld and benchtop) for test and measurement of Luminance, Contrast Ratio and Gamma (Gray Scale/EOTF).

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uLUX Illuminance Meters

This lux meter bundle combines a high-performance photopic sensor with an optical diffuser to provide simple and accurate measurement of illuminance in units of lux (lx), or lumens per square meter. The diffuser provides a ‘cosine correction,’ making the sensor’s illuminance response nearly independent of the direction of incidence.

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Photometric Sensors

UDT Instruments produces precision photometric sensors for diverse applications and are ideally suited for OEMs and value-added resellers. UDTi photometric sensors provide industry leading accuracy, with an unsurpassed ability to match the human eye’s sensitivity to color and light intensity. Each sensor from UDT Instruments includes a NIST-traceable calibration from our NVLAP accredited laboratory (NVLAP Lab Code 200823-0).

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uLUM-MF Photometer

The uLUM-MF is a powerful and flexible system for research labs, metrology centers, and other laboratories that must provide a diverse range of photometric measurements. This bundle combines a four-channel benchtop optometer with four different types of photometric sensors, to provide measurement capability in each of the following fundamental measurement geometries: Luminous Flux (lumens); Illuminance (lux); Luminous Intensity (candela); Luminance (nit; cd/m2).

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What is Photometry?

Photometry involves the measurement of electromagnetic radiation in terms of luminous power – that is, its capacity to stimulate the human visual system and to be perceived as light. Different applications require different types of measurements, and therefore, different types of photometric instruments (photometers).

Photometric quantities include: luminous flux – in lumens (lm), luminous intensity (lm/sr), illuminance (lm/m2) and luminance (lm/m2sr).

  • Luminous Flux Measurements (in units of lumens) are performed with a luminous flux meter. This type of testing is typically used for characterizing the total output of sources such as: LEDs, Lamps and Fiber-Optic Illuminators
  • Illuminance Measurements (in units of lux) are performed with a lux meter. This involves the measurement of the amount of luminous flux incident upon a surface, per unit area. Such measurements are important in the following fields: Architectural and Medical
  • Luminous Intensity Measurements (in units of candela) are performed with an instrument that may be described as a luminous intensity meter or a candela meter. This type of testing is typically used for characterizing the output of a relatively small source in a particular direction. Typical devices under test include: LEDs, Automobile Headlamps and Signal Lamps
  • Luminance Measurements (in units of nits, or candela per square meter) are performed with a luminance meter. This involves measuring the light emitted in a particular direction by a given spot on the surface of a relatively large, or extended source. Typical devices under test include: Computer Monitors, Television Screens, Avionics Displays and other Electronic Displays
Download Our Free Guide to Photometry

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